Hydraulic brake system



July ll, 1950 H. E. slMl HYDRAULIC BRAKE SYSTEM 2 Sheets-Sheet 1 Filed OOb. 50, 1944 July 11, 1950 H. E. slMl 2,514,421

HYDRAULIC BRAKE SYSTEM Filed 001". 50, 1944 Sheets-Sheet 2 Patented July 11, 1950 l 2,514,421 mimmo BRAKE ss'rm Hendrick n. simi, Feniaie, Mien., mmm to The 'limiten-Detroit Axle Company, Detroit,` Mich., a corporation of Ohio Application October 30, 1944, Serial No. 561,122

6 Claims. (Cl. 18S-152) 'Ihis invention relates to improvements in vehicle brake hydraulic systems and has particular reference to improvements in brake hydraulic systems that include a booster pump actuated by some moving part of the vehicle and brought into effective operation upon normal manual manipulation of the vehicle brake controls.

Such a pump acts as a pressure booster for the brake operating fluid and increases the pressure acting on the wheel cylinders without requiring any additional pedal pressure. The pump pressure is. however, at all times under the control of the brake pedal so that the pressure acting on the brake wheel cylinders is under the control of the vehicle operator. Y

Such booster pumps have heretofore been mainly operated by engine driven parts of the vehicle, such as thev vehicle drive shaft. This arrangement is satisfactory where a suitable power take-oil connection is available, but it has been found dilcult to utilize a booster pump system of this type in a towed vehicle such as a trailer or a car or coach pulled by a tractor or locomotive, or in any part of a vehicle not havin a conveniently located power shaft or the like.

In the case of detachable tractor trailer units l particularly, it has been found advantageous to supply the trailer with its own independent brake system to prevent loss of fluid and brake adjustment during coupling and uncoupling operations and also because the trailer brakes must be applied before and somewhat stronger than the tractor brakes to prevent the trailer from "running up on the tractor and jack-kniiing" the vehicle, that is, causing the vehicle to buckle upwardly at the connection between the tractor and the trailer.

'I'he trailer brakes. in such an arrangement, may be operated by the tractor brake 'pedal through a suitable relay, or may be operated by a separate lever disposed conveniently to the operator of the vehicle.

In attempting .to apply the booster pump to a trailer brake system it is found that there is no engine driven power shaft or other convenient rotating power take-off part from which the pump may be positively operated, and the provision of a pump drive shaft drivecoupled to the en-gine would necessitate a complicated and expensive coupling arrangement.

It is conceived, according to a preferred embodimentof the invention, that these problems may be conveniently and economically solved and a satisfactory and dependable trailer brake ybooster system provided by actuating the booster pump directly from a part of the trailer which its preferred embodiment wherein a booster pump is driven from one of the trailer wheels, but it will be understood that this will be illustrative only of the invention which in its broader aspects relates to actuation of the pum-p from any normally idle vehicle-part that is moved in response to movement of the vehicle.

It is therefore the major object of this invention to provide an arrangement wherein a booster pump for a brake hydraulic system is operated directly by a normally idle part actuated by movement of the vehicle, such as a trailer wheel supporting a non-drive axle.

A further object resides in an improved brake hydraulic system of the character indicated wherein a vehicle wheel and wheel mounting structure is constructed and arranged to provide a simple and eilicient support and actuating mechanism for a brake fluid pressure booster A still further object' resides in the provision of an improved brake hydraulic system of the character indicated wherein a booster pump actuated by one wheel of a vehicle serves to control the fluid pressure applied to all of the wheel brake cylinders.

Other objects and advantages will become apparent from the following description in connection with the accompanying drawings and from the appended claims.

, In the accompanying drawings, in which like reference numerals are used to designated similar parts throughout, there is illustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawings however are for the purpose of illustration only and are not to be taken in a limiting or restrictive sense since it will be apparent to those skilled in the art that various changes in the illustrated embodiment may be resorted to without in any way exceeding the scope of the invention.

In the drawings:

Figure 1 is a sectional view of a vehicle, trailer or like, non-driven wheel and wheel mount showing the application of a hydraulic booster pump thereto according to a preferred embodiment o'f the invention;

Figure 2 is a transverse sectional view of the vehicle axle showing the location of the pump relative to the axle: and

Figure 3 is a longitudinal sectional view of a suitable pressure booster pump construction which may be used in the invention.

A hydraulic iluid pressure booster pump, generally indicated at 82, is operatively connected as by conduit 88 to a master cylinder source of hydraulic pressure in a manner which will permit i'iuid to ilow through the pump into conduit 88 which is suitably connected to all of the wheel brake cylinders 'until a predetermined pressure is reached, whereupon the pump is brought into opezation to increase the pressure in conduit 85.

The pump is shown in Figure 3 and comprises a cylindrical body 64 having an internal bore within which a plunger 86 is reciprocable when actuated by a suitable vehicle part such as the wheel driven cam 88 of Figure 1. This plunger has an end portion projecting out of the cylinder for contact with the cam and adjacent to the projectlng end there is a packing seal 88 slidable in a bushing 82 secured in the end of the cylinder bore. At the inner end of the bushing 82 the cylinder bore is enlarged, as indicated at 6I, to receive a compression spring 66. A chamber head 88 is screw threaded into an internally threaded oounterbore in the outer end of the cylinder and is provided with an integral sleeve portion 18 which closely surrounds the plunger 66. A cylindrical spring retainer I2 surrounds sleeve portion 'I8 and has one end upset inwardly and in engagement with an annular shoulder 13 on the plunger, and the opposite end upset outwardly and overlying the outer end of the spring 66, so that when the plunger 66 is moved outwardly or away from chamber head 68, spring 66 will be compressed. Plunger 56 is provided intermediate its length with passages 14 leading to a central well or bore 'I6 which includes valve seat 11 for spring biased poppet valve 18 which limits the direction of ilow of uid through the bore 'I6 to the direction from the passages 'I4 to the outer end oi the bore. Valve 'I8 is urged into seating relation with seat '11 by compression spring 'IS which has for its abutment apertured sleeve 8| screw threaded into the open end of bore 16, said apertures providing iluid passages.

Chamber head 68 is provided with a well or bore 88 communicating with the end portion of the interior of the inner cylinder 'I8 and including a spring biased poppet valve 82 disposed between the end of the inner cylinder and an outlet port 84 which connects through conduit 85, Figure 3, with the wheel brake cylinders.

Passages 'I4 connect through the open end of sleeve 18 and suitable registering apertures in springretalner 12 with the space containing spring 66, which space is connected .through port 86 with iiuid conduit 89 from the brake master cylinder. An air bleed port 95 normally closed by a plug is provided for bleeding air from the pump when the system is filled.

With this construction, fluid from the master cylinder may enter through port 86 into the space containing the spring 66 and from this space may pass through the passages 14, the central bore 16, the check valve 18, the check valve 82 and bore 88, and through the opening 88 to the wheel brake cylinder conduit. The spring 66 will maintain plunger 56 out of contact with cam 58 during the initial stage of brake application and until the iluid pressure in the space at the closed end oi' sleeve 18 is suillcient to overcome the force of spring 66 and move the plunger into contact with the cam. When the plunger contacts the cam,.the piston will begin to reciprocate in the 76 56 extends through the mechanism oi the eor- 4 sleeve 18 and will pump iiuid from the opening 88 to the opening 8l thereby increasing the fluid pressure applied to the associated brake'wheel cylinders.

Figures i and 2 show a preferred arrangement for operatively mounting the booster pump 82 for operation by a wheel'of a trailer vehicle.

The trailer axle 88 is shown as mounted in a suitable hanger 82 secured to a supporting bracket 88. The axle is held against rotation and transi'ers the vehicle load tothe road wheels, one of which is generally indicated at 86. The wheel 86 has a hollow hub portion 88 iournalled by suitable bearings, such as the spaced roller bearings |88 and |82, on the wheel bearing end portion or spindle portion |88 oi! the axle 88, the hub being maintained in operative position on the spindle by suitable means, such as the thrust washer |86 and nuts |88 and ||8 screw threaded onto the reduced end of the axle.- The hub 98 carries an annular brake drum ||2 the open end of which is covered by a suitable dust shield or backing plate H8 centrally apertured to receive the end portion of the axle and secured around the aperture to a brake support ilange H6 welded or otherwise rigidly secured to the axle 88 and extending radially therefrom.

An aperture is provided in the ilange ||8 and A the outer end of the plunger 58 of pump 62 is extended therethrough. Pump body 54 is provided with a ilange surrounding the cylinder bore and this ilange is apertured to receive suitable bolts or screws. as indicated at H8, which extend into suitable screw threaded apertures in the flange 6 and have heads bearing against the outer side ci flange 55 to secure the pump ilrmly in place on the brake supporting ilange H6. In the form illustrated four bolts are used to secure the cylinder to the brake flange.

In securing cam 58 to the hub, a reduction is preferably ilrst provided on the outer surface of the hub end, the diameter of which is slightly greater than the internal diameter of the cam band |26 where both the hub and the cam are at the sameI temperature. The annular cam may be heated to an extent suilicient to increase its internal diameter so that it will slide over the reduced hub portion after which the temperatures may be permitted to normalize thereby shrinking the cam tightly and non-rotatably upon the end portion of the hub.

In the form illustrated the cam is provided with a plurality of lobes, as indicated at |24, contoured to intert with the end of plunger 56 and obtain prompt and effective operation of the booster pump 52 when the brakes are applied.

'I'he hub member is provided with an inwardly extending tapered or flared`oll baille |28 which surrounds the annular cam I 24 and projects somewhat inwardly thereof. The end of the housing 52 carries an oil defiector |30 having at the lower side thereof a. lip which extends into the baille |28 so that any oil or brake duid leaking past the plunger will be deflected into the baffle |28 and will not get into the brake mechanism or on the brake lining.-

The brake mechanism may be of any suitable form, such, for example, as that shown in United States Letters Patent No. 2,337,070, in which case it would include shoes, as indicated at |36, and shoe actuating levers, as indicated at |32, and one of the wheel brake cylinders operatively* associated with the levers. The pump plunger by compression spring 66.

responding brake between the levers and does not interfere in any way with the brake mechanism.

Operation Plunger 56 is normally out of contact with cam 58 since plunger 56 is urged to retracted position When the operator applies the brakes, fluid from the master cylinder is forced through into the pump inlet connection 86 from which it nofws past valves 16 and 82 to pump outlet connection 84 and thence through conduit 85 to the-.wheel brake cylinders. The initial flow of hydraulic fluid takes up the slack in the brake mechanisms and brings the brake shoes firmly into contact with the corresponding brake drums. Continued application of the master cylinder pressuref becomes effective within the chamber between chamber head 68 and the adjacent end of plunger 56 to displace the plunger outward again'stj the force of spring 66 and into contact with cani 58 which rotates with wheel 86 when the vehicle is in motion. As cam 58 forces plunger 56 back, valve 18 will close and the plunger will forcethe fluid in the chamber out past valve 82 which'will close against return flow of the fluid. Pump operation is controlled by master cylinder pressure and will discontinue when that is interrupted.

'I'he invention may be embodied in otherspecific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered ingall respects as illustrative and not restrictive, the scope of the invention being indicated by the -appended claims rather than by the foregoing description, and all changes which come within lthe meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured' by United States Letters Patent is:

1. In combination with a vehicle axle having a brake support nange thereon and a wheel hub journalled on said axle at one side of said flange; a hydraulic booster pump projecting through van aperture in said flange; and a cam on said hub for operating said pump.

2..,jl'hecombination defined in claim 1 wherein said pump has a plunger extending through said aperture and a cylinder secured to said brake 3. The combination dened in claim 1 wherein said pump is a reciprocating type pump and said cam is an annular face cam having lobes extending parallel to the axis of rotation of said hub.

4. The combination as defined in claim 1 wherein said brake support flange carries friction brake mechanism and said pump extends through said brake mechanism.

5. In a vehicle brake' assembly, an axle, a ground engaging wheel journaled on said axle, an annular cam rigid with said wheel and having a plurality of inwardly facing peripheral lobes, a booster pump mounted on a stationary support adjacent said wheel, and a piston rod reciprocable parallel to the axis of said wheel projecting from said pump and normally disposed out of contact with said cam but adapted to be advanced into contact with said cam lobes for actuation thereby under control of the vehicle operator.

6. In combination with a vehicle axle, a wheel hub journalled thereon having a brake drum, hydraulically operated friction brake mechanism mounted on the axle within said drum, a support for said brake mechanism and a hydraulic booster pump having a reciprocable plunger in substantially axially parallel relation with the axle mounted on said support, and means carried by said wheel hub and operable in the rotation thereof to actuate said pump plunger.

HENDRICK E. SDI.V

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,529,097 Tucker Mar. 10, 1925 1,610,755 Decker v.' Dec. 14, 1926 1,749,495 Macpherson Mar. 4, 1930 2,107,257 Beusch Feb. l, 1938 2,396,879 Stelzer Mar. 19, 1946 FOREIGN PATENTS Number Country l Date 311,255 Great Britain May 7, 1929 364,659 Great Britain Jan. 11,1932 

